CHW,
Definately link up with Fleep up north, you'll have a great time.
It truly is hit-and-miss this time of year in the Spfld region. Most divers around here either are not equiped (becuase of cost) to dive the cold or simply do not desire to dive the cold. I've been known to brave the cold before, but my gear is being serviced for a trip in January, so I would be stuck renting (not that I can't). Oronogo should be shut down already, but with the warm trend, who knows.
Feel free to contact Mike (my boss) from Sho-Me Scuba (Springfield) to see if he might be available for a lake run and what he might charge. 417-882-3483
Also, I am hitting up Diver's Unlimited International about the DOG Days Dry Suit Rally 2008, so I can get the calendar posted ASAP. Forward planning for April!